Paper forming assembly and method



E. J. JUSTUS ET AL PAPER FORMING ASSEMBLY AND METHOD May 7, 1968 sSheet-Sheet 1 Filed June 28, 1965 INVENTOR. @4242 Mdaaraa Q4100 60654-622 BY ATTORNEYS y 1968 E. J. JUSTUS ET AL 3,382,143

. PAPER FORMING ASSEMBLY AND METHOD Filed June 28. 1965 a Sheets-Sheet 224 m INVE "r012.

2a {6 Z2442 L/ (/9705 8% ATTORNEYS May 7, 1968 J, JUSTUS ET AL PAPERFORMING ASSEMBLY AND METHOD 8 Sheets-Sheet 3 Filed June 28, 1965 K IIQINVENTOR. Z2424? k/ /z/svaa 5414p @flVfi/SO/V ATTORNEYS May 7, 1968 E.J. JUSTUS ET PAPER FORMING ASSEMBLY AND METHOD 8 Sheets-Sheet 4 FiledJune 28, 1965 Z2414? J 5414; Ga a/190w aux 7&3 W ATTORNEYS \M; w k 3%QQR QQM QQQN May 7, 1968 E. J. JUSTUS ET AL 3,382,143

PAPER FORMING ASSEMBLY AND METHOD Filed June 28, 1965 8 Sheets-Sheet 5INVENTOR. [24242 J Wsvva 541/0 @anvfw/l 5% BrM/ Z @W ATTORNEYS May 7,1968 E. J. JUSTUS ET AL 3 3 PAPER FORMING ASSEMBLY AND METHOD Filed June28, 1965 8 Sheets-Sheet 6 INVENTORS [2546 L/ /z/araa 54w @wW/IQOA/ BYATTORNEYS May 7, 1968 E. .1. JUSTUS ET AL PAPER FORMING ASSEMBLY ANDMETHOD 8 Sheets-Sheet Filed June 28, 1965 WHY Maw; M a v ATTORNEYS May7, 1968 E, J JUSTUS ET AL 3,382,143

PAPER FORMING ASSEMBLY AND METHOD Filed June 28, 1965 8 Sheets-Sheet 8.EIE- 9 INVENTOR. [2942 J k/asvz/s @41/40 @aemfeo/v m'w mu/ w/fi wATTORNEYS United States Patent Oflice 3,382,143 Patented May 7, 19883,382,143 PAPER FORMING ASSEMBLY AND METHOD Edgar J. Justus, Beloit,Wis., and David R. Gustafson, Rockton, 111., assignors to BeloitCorporation, Beloit, Wis, a corporation of WisconsinContinuation-in-part of application Ser. No. 412,909, Nov. 23, 1964.This application June 28, 1965, Ser. No. 467,664

9 Claims. (Cl. 162-303) ABSTRACT OF THE DISCLOSURE The present inventionrelates to a plural wire web forming device wherein a web forming zoneis defined between converging forming wires by the use of curved,stationary, permeable guide means acting against one wire to urge suchwire through an elongated substantially curved path and into convergencewith the opposite wire under tension. This is a continuation-in-part ofour application Ser. No. 412,909, filed Nov. 23, 1964.

The present invention relates to improvements in paper making machineryor the like, and more particularly, in improvements in devices andmethods for forming the initial web of fibrous material from a diluteliquid suspension in paper machines or the like.

Although the instant invention is particularly adapted for use in theforming arrangement of paper making machinery and it will be describedprimarily in connection therewith, it will be appreciated that theinvention has other uses in related devices. Essentially, the instantinvention is concerned with a new and unique forming arrangement which"has been devised by us for such purposes as accommodating higher papermaking machinery speeds as well as improved quality in the paper somade. It will be appreciated that the very substantial capitalinvestment in paper making machinery makes it necessary for continuousresearch and development in improvements in not only paper makingquality but operating speeds for such machinery. The instant inventionprovides a novel arrangement and method for effecting improved papermaking quality at high speeds.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

FIGURES 1A, 1B and 1C are elevational views shown in the sequence ABC ofa paper machine forming section embodying the instant invention and itwill be appreciated that these three views may be referred to as asingle embodiment of a forming unit;

FIGURE 2 is a fragmentary enlarged detail view of an upper foil suctionbox taken generally along the line 11-- II of FIGURE 1B, with partsbroken away or not shown for purposes of simplification; and

FIGURE 3 is a side elevational view taken generally along the sideindicated at III-III of FIGURE 2 showing in side elevation generally thespecific aspects of the foil suction box employed in the practice of theinstant invention;

FIGURE 4 is an elevational view, with parts broken away and parts shownin section of an inlet or headbox for use in the practice of theinvention;

FIGURE 5 is an essentially diagrammatic fragmentary cross-machinesection, with parts broken away and parts shown in section, takengenerally along the line of the roof of the inlet of FIGURE 4, such linebeing indicated at V-V;

FIGURE 6 is an essentially schematic view shownin elevation tocorrespond to the elevational view of the inlet indicated in FIGURE 4,but again with certain parts broken away, and the view of FIGURE 6 isintended to represent generally the variations in cross sectional areaof the controlled thin portions of the stock inlet;

FIGURE 7 is a fragmentary detail enlarged view of certain essentialelements in the central portion of the narrow stock inlet of FIGURE 4,taken approximately from the same view as that shown in FIGURE 4, butshowing these essential elements in enlarged elevation and section;

FIGURE 8 is an essentially diagrammatic top plan view of a cross-flowheader for stock for the inlet of the embodiment of the instantinvention;

FIGURE 9 is an essentially diagrammatic elevational view showing theoverall inlet assembly of the instant invention taken generally from therear side of the inlet; and

FIGURE 10 is an essentially diagrammatic view comparable to that ofFIGURE 9 but showing still another embodiment of the instant invention.

As shown on the drawings:

In FIGURE 1A, the reference numeral 10 indicates generally a high speedstock inlet which consists essentially in means for generating andfeeding a thin generally horizontal high speed stock jet ofsubstantially homogeneous suspended entangled co-moving stock fibers onto a bottom wire reach here indicated at 20, of a forming wire that istrained around an initial turning and drive roll 21, a breast roll 22,and a couch roll shown at 23 in FIGURE 1C, each of which rolls 21, 22and 23 being mounted on appropriate bearings which in turn are mountedon conventional framing indicated generally at 24 in the views ofFIGURES 1A, B and C, but without showing specific details of the bearingmountings for the various rolls mentioned, since such aspects ofmounting forming wire 20 and supporting rolls are old and well known inthe art. In addition, it will be noted that the forming wire passes fromthe breast roll 22 to the couch roll 23 over a plurality of suctionboxes SB-l through SB-S which are of well known structure and whichfunction to exert a subatmospheric pressure to the underside of theforming wire 20 while the stock and/or web is moving on the forming wire20 for purposes of dewatering the same in a function that is old andwell known to the skilled workers in the art. The framing support forsuch suction boxes SB1 through 5 is indicated in part at 24a and 24b inFIGURES 1B and 1C, for purposes of showing the general arrangement,although specific details thereof are also fully understood by theskilled workers in the art.

In addition, the framing support for the initial suction box SB-1 shownin FIGURE 1B carries a cross-machine frame 24c which mounts a foil 25that engages the underside of the forming wire 20 for relative movementtherebetween, the foil 25 being maintained stationary, but for purposesof supporting the underside of the forming wire 20 and at the same timeassisting in the removal of droplets of water tending to collect on theunderside of the forming wire 20 in the region of the immediateoff-running side of the upper foil box, indicated at 30 and shown ingreater detail in FIGURES 2 and 3. The structure of the foil 25 is wellknown to those skilled in the art and is provided with a rounded forwardedge 25a for initial engagement with the underside of the wire 20followed by a generally flat or planar surface which gradually separatesfrom the underside of the wire 20 through a relatively small angle ofabout 5 for purposes of generating a pumping effect to assist in waterremoval. This particular function of the foil 25 is old and well knownat the present time in paper making machinery. It will be noted,

however, that the foil 25 is mounted on shims or other suitable devicesto afford vertical adjustment therefor indicated diagrammatically by thetwo-headed arrow at A in the support pedestal 240 of FIGURE 1B. Therelative vertical adjustment of the foil 25 is also carried out bystructures understood by the skilled workers in the art, and istherefore indicated diagrammatically by the twoheaded arrow A, althoughit will be appreciated that such relative vertical adjustment of thefoil 25 has certain functions in the practice of the instant inventionwhich will be described in greater detail hereinafter. Also, it will benoted that at the bottom of FIGURE 1B there is shown fragmentarily awire tensioning roll 26 with adjustable means indicated also by a doubleheaded arrow designated A for purposes of adjusting the overall tensionon the forming wire 20, as it is used in the practice of the instantinvention. It will thus be seen that the relative position of the wirereach 20a between the top of the breast roll 22 and the top of the foil25 is controlled not only by the adjustable positioning of the foil 25but also the adjustable tensioning on the wire 20 by the tension roll26, both of which adjustable devices are understood by the skilledworkers in the art and need not be described in further detail herein.In fact, the breast roll 22 itself may be mounted adjustably (asindicated schematically by the double headed horizontal and verticalarrows AA at the bearing B) for additional facility in adjusting theoverall position of the wire reach 20a which moves generally in thelongitudinal direction or in the direction of stock and web movement.

Referring again to FIGURE 1A, it will be seen that the device forgenerating the previously described thin stream of the high speed stockjet is indicated essentially diagrammatically at 10 with an internalpassage of crossmachine width being shown diagrammatically at 10:: forpurposes of indicating the location of the stock stream jet beinggenerated. It will also be noted that the overall stock inlet 10 ismounted on suitable bottom framing indicated at 11 plus upright framingindicated at 12 and 13 for carrying the horizontal slice jet generatingand defining means indicated at 14a and 14b, feeding stock from asuitable source indicated at 15 into which stock is fed at a controlledrate by a suitable stock flow device such as a fan pump indicateddiagrammatically at F in FIG- URE 1A at a rate sufficient to generatethe desired speed and other properties in the stock jet flowing inpredetermined manner out of the stock jet opening indicated at 14 inFIGURE 13. The stock jet generating device 10 herein indicated inessentially diagrammatic form is known to prior workers in the art andwell understood thereby and need not be described in further detail,except to mention various patent disclosures hereinafter which describesuitable means for stock jet generation useful in the practice of theinstant invention. It Will be noted, however, that the overall stock jetgenerating device 10 here shown is indicated diagrammatically asgenerating a substantially horizontal stock jet stream at the sliceoutlet 14 of FIGURE 1B at substantially the top of the breast roll 22.It will be appreciated, however, that certain limited adjustment of theposition of the breast roll 22, via the bearings B thereof may beafforded, as indicated by the two-headed arrows AA; but it is generallypreferable to provide for limited adjustment of the stock jet generatingdevice 10 itself for purposes of the instant invention and this may bedone by spaced vertical adjusting devices indicated by the double headedarrows A-1 and A-2 as well as a suitable horizontal adjusting deviceindicated by the double headed arrow at A-3, all of which adjustingdevices are again means that are well known and understood by theskilled workers in the art, but because of the general size of themachinery are sufficiently complex in size and character to make theshowing of the same diagrammatically advantageous in clarifying andsimplifying the showing of the essence of the instant invcntion herein.

Referring specifically to suitable stock jet stream generating devicesuseful in the practice of the instant invention in the position of or asa complete substitute for the device here indicated at 10, reference ismade to certain patent and application disclosures, each of which isincorporated herein by reference, which include US. Patent No. 3,098,787and Parker et al. Ser. No. 338,424, filed Jan. 17, 1964 (and the earlierapplications referred to therein, all of which are owned by the assigneeof the instant application). In essence, each of these variousdisclosures and a number of other prior art disclosures have shownvarious turbulence generating devices which, in the present diagrammaticshowing would be located in the section indicated at 14a or upstreamthereof and would be used essentially for initially effecting a completedistribution of discrete individual fibers in the dilute stock beinggenerated for high speed feed through the continuous channel 10a hereshown diagrammatically extending through the sections 14a and 14b ofFIGURE 1A. It will be appreciated that the essence of the stock jet orstock stream generating channel or device 10 involves the creation of aninitial turbulence of one type or another upstream in the region of thechannel 10:! for adequate fiber distribution followed by a low scalemuch more moderate type of turbulence which is intended to maintain thefibers in their own discrete distributed condition while the same timefeeding the dilute fiber distribution at extremely high speed ultimatelyon to the forming wire, previously indicated at 20a. The thin stream isof only approximately from inch to 1 /2 inch in height, depending onbasis weight and grade of paper, in the region of the slice 14' as it isfed from the channel 10/) at an extremely high velocity (in theneighborhood of 2500 to 3000 or more feet per minute) at the requisitehigh pressures and in the generally horizontal or longitudinal directionaligned with the direction of an imaginary reference (abscissa) line,which is indicated at the line 200 in FIGURE 3 hereof. The line 200 isan imaginary straight line drawn in a tangent plane generally from thetop of the breast roll 22 at substantially the slice exit 14- andextending to the top of the foil 25. Since the wire 20 is not withoutsome elasticity and flexibility, no matter how much tension is placed onthe wire by the roll 26 or otherwise, it will be appreciated that thewire 20 will have a tendency to be forced downwardly slightly below thisimaginary line 200 by the force of the stock on the top thereof, but oneof the important objects of the instant invention involves maintenanceof the forming wire 20 at a relatively high tension by the use of thetensioning roll 26 or other conventional devices so that the bottomreach 20a of the forming wire between the breast roll 22 and the foil 25is here shown being maintained substantially planar, i.e., the line 20aappears to be substantially a straight line as indicated in FIGURE 1Band thus to align substantially with the imaginary straight line 200 ofFIG- URE 3 by virtue of the maintenance of the high tension therein. Thedevice 10 provides the stock feed conduit 10a and associated operatingelements (all understood by the skilled workers in the art) forgenerating and feeding a thin high speed stock jet (at approximately 14)of substantially homogeneous suspended entangled co-moving stock fibersin dilute aqueous system, which stock jet is fed on to the Wire reach20a at approximately the top of the breast roll 22 and the stock jet issubstantially commensurate in transverse dimension and longitudinalspeed to that of the wire reach 20a at the immediate vicinity (14) atwhich the stock jet is fed on to the wire reach 20a and the stock jet isaligned and fed on to the wire reach 20a in substantially the samegenerally horizontal direction of the movement of the initial Wire reach20a. It will be appreciated that, if the general direction of the wirereach 20a is to be altered normally from a horizontal direction (e.g. byrelative adjustment of the breast roll 22 and the foil 25), thenadjustment of the various devices A--1 through A-3 for the stock streamgenerating device is also carried out in order to maintain the desiredgeneral alignment of the stock stream jet at 14 in substantially thedirection of the forming wire reach 2011 which for practical purposesshould not vary outside of about 30 from a generally horizontaldirection to be consistent with the preferred operation of the instantinvention.

In summary, then, it will be seen that the high speed stock jet at 14flows on to the top of the forming wire 20 at substantially the top ofthe breast roll 22 or at least plus or minus about 10 or from thevertical center line 22CL for the breast roll 22 supporting from beneaththe forming wire 20.

As also indicated in FIGURES 1B and 1C, in the embodiment of the instantinvention there is provided an upper forming wire which is indicatedgenerally by the reference numeral 40. The upper forming wire 40 travelsbeneath and is supported on the top side by the foil box 30 in theapproximate region of the jet outlet 10b (as indicated in FIGURE 1B),and it also travels around appropriate guide and tensioning rollsindicated at 41, 42, 43, 44, 45 and 46. Although shown essentiallydiagrammatically, it will be seen that the horizontal framing 24 is alsoprovided with upright frame elements 24d, 24a and 24 with thelast-mentioned upright 24 supporting the guide roll 46 for rotation andseparation of the forming wire 40 from the formed web W which is carriedaway on the lower forming wire 20, as shown in FIGURE 1C. The uprightsupport 24f is also the principal support for a couch press defined bythe plain bottom couch roll 23 supporting from beneath the forming wirewith the web W thereon and an upper couch press roll 47 within the loopof the upper wire 40 which is carried at opposite ends on fixed 47a andmovable 47b pivots, with the movable pivots 4719 being in turn attachedto a suitable power cylinder 47c that is in turn connected to a lowerextension of the framing at 241i for purposes of controlling the load atthe couch nip N, which is the nip defined between the forming wires 20and 40 and plain press rolls 23 and 47 for purposes of removing excesswater at the location of the nip N by mechanical means, prior tosubsequent treatment of the web W as it is fed into the rest of themachine on the forming wire 20. The advantages of a couch press 23-47are apparent to the skilled worker in the art; but the successful use ofthe same heretofore has been limited, if possible at all, for the reasonthat it is necessary to have a reasonably strong web formation prior tothe application of any pressing action for dewatering thereof and Websof this strength were heretofore ordinarily not possible at such anearly stage in the forming operation (or so closely spaced from thestock jet slice 10b) as here indicated. As will be explained in greaterdetail hereinafter, the initial forming arrangement includingparticularly the top foil suction box 30 is so constructed as to afforda maximum rate of dewatering and a maximum rate of strong web formationmaking possible the use of the couch press 2347 here shown.

Referring again to FIGURE IE, it will be seen that the upright frames24d and 2% are provided with appropriate cross frames 2412 and 24g, allof conventional structure which the skilled worker in the art willunderstand are positioned (as in the case of all of the framing hereindicated) at opposite sides of the forming wires 20 and 40 so as tomount opposite ends of the functioning devices herein described. It willthus be seen that a bearing pedestal 242a is indicated as being mountedon the upright 24:: for the purpose of mounting the wire guide roll 45.A bearing pedestal 24dd is shown as an extension of the upright 24d formounting the guide roll 42; and a bearing pedestal 24xx is shown mountedon the side of the upright 24d for mounting the guide roll 41. Inaddition, it will be noted that conventional jackscrew assemblies 18 1and JS-2 are shown mounted on the top cross frame 24g for suitableadjustment of the guide and tensioning rolls 43 and 44, respectively. Itwill be noted that the double headed arrows indicated in each case at Aindicate approximately the direction in which adjustment is afforded forthe rolls 43 and 44 so that these rolls may be used effectively to guideand tension the upper forming wire 40, again in an essentiallyconventional manner which need not be described in further detailherein, since it is well understood by the skilled workers in the art.

In addition, it will be seen that the specific lower portion of the foilsuction box is actually mounted in a housing 31 which is pivotallymounted at its forward end on the previously described pedestal 2 4xxand is adjustable in a generally vertical direction by the use of ajackscrew indicated at 18-3; whereas the rear end of the housing 3'1 ismounted on a depending frame 241th carrying a jac'kscrew JS-4 which isadapted for limited vertical adjust-ment or movement as indicated by thedouble headed arrow A. The jackscrews JS3 and JS'4 thus provideconventional controlled means of adjustment for effecting overallvertical movement as well as relative tilting of the housing 31 and thelower functional portion of the foil suction box 30 which actuallycontacts the inside of the loop of the forming wire 40. It will be apreciated that a side suction takeoff 33 is provided at the rear end ofthe housing 31 (although indicated essentially diagrammatically) with anappropriate overflow dam indicated at 35 within the housing 31, so thatwater drawn up through the foil suction box 30 will fall over the dam 35and be withdrawn from the side of the machine through the suctiontakeoff 33 in substantially the manner of operation employed for waterand air removal through suction box takeofis which are, of course,employed in connection with the suction boxes SB-l through "5hereinbefore described. The dam 35 will, of course, tend to control tosome extent the water level continuously accumulating in the lowerportion of the upper suction box housing 3 1, whereas the top side ofthe housing 3 1 is closed and maintained at subatmospheric pressure byvirtue of the suction takoff 33.

It will be noted that the forming wire travels downwardly around theguide roll 41 and then around a curvate solid surface or shoe indicatedgenerally at which aligns the same for its travel in guided fashionalong the bottom of the longitudinally spaced crossmachine foils in thefoil box 30 indicated at 51 through 60. It will be seen that theindividual longitudinally spaced cross-machine foils 51 through areshown in an elevational view in FIGURE 3 (through the side wall 30a ofthe bottom foil box 30 and fragment'arily in a top elevation in FIGURE2); and, in contrast to the previously described foil 25, the structuresof the foils or blades 51, 52, etc. are different, and these foils 5'1,52, etc. have individual structures such as those shown substantially inVan Ryzin US. Patent No. 2,740,332 (wherein Van Ryzins fiat wirecontacting edges are uniplanar instead of the generally curvedlongitudinal contour which the flat wire contacting edegs 51a, 52a, etc.define in the foil box 30 of the invention). Referring generally to thegenerally thin flat structure and edgewise arrangement of a single foil,attention is directed to the foil 52 which is indicated by way ofexample in both FIGURES 2 and 3 as the second foil in the longitudinallyspaced arrangement. It will be seen from FIGURE 2 that the thin top edgeof the foil 52 is shown at 52x in full view extending from the top edgeof the side wall 30!: of the .foil box 30. It will also be seen that adeckle or sealing piece 3% is shown in FIGURE 2 as being attached to theside wall 30a and is shown in FIGURE 3 as extending along the bottom ofthe side Wall 30a and having a general-curvate bottom surface which ismore pronounced at the forward or left hand end 3012b thereof.

In top plan view only the portion indicated at 30b being visible at theforward end and the top plan portion 30b" being visible at the rear orright hand end of the sealing piece 3% in FIGURE 2, with the remainderthereof being shown covered at least in part by the various slantedfoils d through 60. It will also be noted that the foils 5 through 60extend downwardly from the top exposed thin edge portions 51x through60x shown in FIGURE 2 down to thin edge bottom portions 51b through60']; each of which engages and is secured to the top of the sidesealing strip 30b indicated in FIGURES 2 and 3.

It will further be seen that the central portion of each of theindividual foils 51 through 60 extending downwardly beneath the sealingedge 30b (which is shown on one side only in FIGURE 2, but which will beunder stood to be present at opposite sides of the foil box 30 in acomplete view) extends downwardly to engage the top side of thetraveling wire 40 along a smoothly machined (i.e. mirror finished)guiding surface or edge 51a through 60a indicated for the bottom of eachof the foils 51 through 60. Thus, referring again to the foil 52 inFIGURE 2, it will be seen that the top edge 52x is shown and this foil52 then extends from the top edge 52 downwardly and to the left to asurface 521; along the edge thereof which engages the sealing strip 3%and to a surface which is indicated farther to the left in FIGURE 2 at52a which engages the inside of the loop at the top wire 40 and controlsthe position thereof. The extreme bottoms of the foils 51 through 60, atthe polished (i.e. preferably to a mirror finish, per Walker Ser. No.150,917, filed Nov. 8, 1961, as preferably are all elements engaging therelatively moving wire smooth guide surfaces 51a through 60a, will ofcourse furnish relatively closely spaced (in the longitudinal direction)edge supports for the wire 40, which supporting edge surfaces 51athrough 60a will be found upon examination of the substantiallyelongated curvate contour of the upper wire (as shown in thelongitudinal contour of FIGURE 3) to define generally spaced loci ofnoncircular elongated curve with (convex) reference to the theoreticalor imaginary straight (abscissa) line 200 herein before discussed.Beneath the suction box 31,, the foil box 30 is framed by conventionalremoval seals, i.e., a sealing rear piece 31a, with an appropriateflange 31b to afford means for securing it to the foil box 30 (asindicated in F IGURES 2 and 3); whereas FIGURE 1B shows a front roundedcrossmachine sealing piece 50 with seal shim 31c that is secured to theforward or left end of the foil box 30 (FIG- URES 2 and 3); and amachine-side sealing piece 31c (counterpart of a drive side piece notshown) is seen partially in FIGURES 1B and 2 (although these areessentially omitted from other views for purposes of simplicity) tocomplete the peripheral seal for the foil box 30. The forward shimsealing piece 31c, of course, has a lower smooth bearing surface 310(abruptly terminating at its off-running edge line 30bb) that forms acontinuation for the initial guide surface for the wire, previouslyindicated at 50 in FIGURE 1B, and this overall surface 50, 31c ispreferably generally cylindrical in contour (and abruptly terminating at301112) for smooth movement of the wire thereover and feeding of thewire 40 in smooth uninterrupted manner directly on to and over thespaced smooth bottom guide surfaces of the stationary foil edges 51athrough 60a which also terminate abruptly at the off-running sidesthereof (as contrasted to gradual divergence as described for the foilin order to separate abruptly from the traveling wire 40 so as topreclude localized pumping effect pressure variations drastic enough todamage web formation on the wire 40.

In reference to completion of the details indicated in FIGURES 2 and 3,it will be noted that the rear flange 31b and the side piece a, 312 forthe foil box 30 are provided, at the places indicated at B, withsuitable apertures for receiving threaded bolts for securing the foilbox 30 and peripheral seal 312, etc. to the bottom of the overallsuction box 31 in the conventional manner.

The significant feature of the overall bottom contour arrangement of thefoil box 30 involves specifically a reference to an elongated curve thatis based generally upon a theoretical abscissa lying along the imaginaryline 2% hereinbefore described in which the increment thereof will beindicated by the reference letter D shown with a two-headed arrow inFIGURE 3; and an ordinate indicated generally by the center line CL inFIGURE 3 in which the increments thereof will be indicated by thereference letter H also indicated by a two-headed arrow in FIGURE 3. Theintersection of the abscissa 200 and the ordinate CL is the theoretical0, 0 for the curve:

(which. representing the box contour per se will stay within the limitsherein prescribed for the constants C and k, during desired operationnotwithstanding tilting of the foil box 30 and/or inlet 10 via theadjustments A, A, to the limited extent contemplated) wherein H is thedistance (in inches) vertically up from the line 200, D is the distance(in inches) to the right indicated at D through D of FIGURE 3, or in thepositive direction from the line CL, as shown in FIGURE 3; and C and kare constants. It will be understood from FIG- URES 1B and 3 that thetop wire is there shown in a position where it is fully supported fromabove by the smooth surfaces and 31c which feed the same to a point P(FIGURE 3) on the ordinate CL; and prior to the point P to the backingsurfaces 50 and 310 make the wire 40 impervious or Water impermeable. Atthe leading foil edge 51a, i.e., the next point P (and, of course, atthe slightly higher point P the height H of the wire 40 above theabscissa 200 (shown in exact longitudinal alignment with the wire 20 onthe breast roll 22 in the specific arrangement of FIGURE 3) issubstantially the height of the stock jet stream issuing at 14'(assuming the wire run 20a is maintained in substantially theundeflected alignment and spacing shown in the standing arrangement ofFIGURE 3), and flowing at approximately 3000 feet per minute for thepresent embodiment.

In the case of stock flowing between the points P and P which is theinitial unsupported or open area for the wire 40, the wire 40 becomesfunctionally waterperrneable and initially receives water flowing intothe foil box 30. Prior to this region defined by the transverse slotbetween points P and P it will be noted that the solid supports 50 and310 are positioned very closely to the top of the structure 14b for thestock jet inlet 14 (and the wire 40 runs there'between in very closerunning relation) such that substantially the full stock jet pressurewill be exerted against both the top and bottom wires 40 and 20substantially immediately after and/ or at the region P to P withnegligible backward flow and/or loss of pressure by backward stock flowor upward flow back between the inlet structure 1412 and the solidlysupported wire 40. For purposes of the reference, point P will beconsidered as lying in the ordinate CL and the distance from. P to Pwill be considered to be approximately one inch (actually inch). Roughlyspeaking, the curve including the loci P to P must be considered to be agenerally elongated noncircular curvature in its transition from thegenerally cylindrical (or circular in section defined by the cylindricalsolid guiding surfaces 50, 31c) to the elongated curved configurationdefined by the longitudinal contour of the loci of the foil bottoms 51a,etc. but the essence of the curve of the loci of P to P will notnecessarily be curvilinear even though for practical purposes it isinherently curved for aligning the wire 40 with the subsequent elongatedgenerally curved contour of the wire alignment found to be substantiallyessential to the practice of the invention; and the stock jet stream 14will be considered as having substantially the same structure in width,height, speed, etc. as that passing through the center line CL (eventhough it may not exit from its supporting structure 14b at preciselythis point, and, is shown in FIGURE 1B, is obviously upstreamtherefrom). Likewise, the abscissa 200 will be considered as lying in agenerally horizontal plane (substantially perpendicular to the aforesaidcenter line CL) and defining a straight line in substantial longitudinalalignment with the wire run 20a which may be deflected somewhat awayfrom such horizontal plane. For purposes of reference in considering themore essential features of the invention we assume for the moment thatthe line 200 is horizontal.

The critical area in the operation of the forming area is the convergingsheet forming zone immediately after the stock leaves the inlet 14b andis deposited on the bottom wire 20. This zone is the converging nipwhere the top wire 40 approaches the bottom wire 24) and where the wateris drained from the stock slurry both upward and downward, leaving thefiber deposited between the two wires 20 and 40 to form the sheet orultimate web W. The function of the top wire 40 in conjunction with thebottom wire 20, besides providing a spetum through which water can bedrained from the sheet upward as well as downwardly, is to eliminate thefree surface and thus provide stability and control over the slurry asit is being drained to form the sheet. In order for this stability toexist at high speeds it is essential that the forming nip converge insuch a way that the slurly will feel essentially a constant pressure asthe sheet is being formed or until the network strength of the slurry ishigh enough so that an increase in the pressure gradient between thewires 20 and 40 will not have a damaging effect on the sheet W beingformed.

The tests made on experimental forming units have shown that theconvergence of the forming nip is critical. The nip is made bymaintaining tension in the bottom wire 20 (or bottom portion 200) andhaving the top wire drag (also under tension) against the contouredbottom cover of the top forming box as indicated at the longitudinallyspaced surfaces 51a, 52a, 53a, etc. (i.e., the longitudinal contour ofthe loci of such spaced wire-contacting surfaces of edges 51a, 52a, etc.with the driven wire 40 driven through the general longitudinal contourof a multiplicity of short successive short reaches bridging the shortspaces between such edges 51a, 52a, etc. so as to travel substantiallyalong the elongated curve defined by such loci). The critical section ofthe cover or box 30 is machined to a curve H=CD where C and k areconstants determined by the sheet weight, stock freeness andconsistency. The surface of the cover from D= to D=.75 is less criticaland machined so that it forms a smooth transition from the nose piece tothe curve H=CD* The essentially critical surfaces 51a, 52a, 53a, etc.from D=.75" to 6 or 8" (i.e. in the distance indicated fromsubstantially D to about D or D are machined according to the curve H=CDThus, the given formula for the curve is referenced primarily to thelongitudinal contour of the active face or cover of the foil box 30 (andso are the ordinate CL and the abscissa 200 for purposes of definingsuch curve) although the foil box 30 itself is mounted for limitedvertical and pivotal movement in the manner hereinbefore described. FromD=6" or 8" to the end of of the cover the slope of the curve can be madesteeper than H=CD to make use of higher normal forces between the wiresfor increased drainage. This can be done because at D 6" to 8 where thestrength of the formed mat W is high enough so that it resistsdisruption and damage from the increasingly higher drainage pressures.In plotting the curve of H=CD for the relative positions of the elementsin the arrangement of FIGURE 3, the D axis is the theoretically straightline previously indicated at 200, i.e., extending from the top of thebreast roll (bottom wire support roll just ahead of the open portion ofthe forming box) to the top of bottom wire support following the formingbox and the H axis is the line perpendicular to the D axis, i.e.previously referred to as CL extending downward from the initial openingto the vacuum compartment in the suction box 30.

The machined surface of the forming cover now being used on a foil box30 may be considered to be (the longitudinal contour of loci of theblade edges 51a, 52a, etc.) plotted on the graph previously indicated(in FIGURE 3). This is the recommended curve for slow or low freenessstock such as is used for newsprint and coating rawstock. The C and kvalues for the curve H=CD for this surface approximate C=.516 andk=.284. For more free draining stock (lower) k value would increase inthe negative direction and in running at lower consistencies the C valuewould be high to allow for running the greater volume. The ranges forpractical purposes for upper and lower values of C and k that might beunderstood are C=.5 to 1.6 and k=-.2 to .8 for H :CD for the criticalforming area and for the trailing end of the cover the slope of thecurve can deviate from (i.e., may be made or conformed at this stage ofthe curve such that the curve does not tend, e.g., to level out quite asmuch as the elongated curve formula suggests and the, curve may thushave a downward slope steeper than) H CD to make use of higher normalforces between the wires for increased drainage. This can be donebecause at D=6 to 8 the network strength of the formed mat W or web ishigh enough that it resists damage from the increasingly higher drainagepressures.

The essence of the concept here involved seems to be that the stock jetdoes not change in composition, height, width, etc. from its exit fromthe supporting structure 14b to substantially the point P From the pointP to P (which limit the longitudinal demension of the slot which extendsin the full cross-machine direction) there is an initial rapid fiowwhich occurs upwardly (and depending upon the exact position of thebreast roll 22 probably also occurs downwardly simultaneously); but thisis extremely difiicult to control. Roughly speaking the bottom wire 20remains tangent to the breast roll (i.e. substantially horizontal inmost instances) whereas the top wire .0 moves through such loci P Plying in a cylindrical or curvilinear surface of comparatively greatradiusfor a very brief distance of less than one inch (i.e.substantially D and preferably about /1 inch. In these small dimensionsthe wires 20 and 40 function as rigid, inflexible beams, even though acertain and even a substantial amount of drainage may occur (whichdrainage, it will be understood from a practical point of view, does notresult in any appreciable web formation and/ or increase in theremaining stock consistency on the wires 20 and 40). After D equalsapproximately inch, then the drainage and web formation become criticaland the top wire 40 is caused to form the elongated curve:

It must be understood, of course, that downward move ment of the box 30and/or excessive pressures will cause a certain downward dip to thelower wire 20 in this regionperhaps in the nature of a catenary butprobably in an elongated curved forrnalthough means (26, etc.) areprovided for maintenance of high tension thereon and thus a minimum orat least controlled dip between the breast roll 22 and foil 25. Drivecontrols (indicated schematically at M and M in FIGURE 1C) for the twowires 20 and 40 also carry out this function.

The object in this critical region of stock formation is to keepsubstantially the same internal pressure (which is within the stock onboth the top and bottom semiwebs). Hence the stock pressure as well asfoil box alignment are compensated for by the type of dipping which thebottom wire 20a may tend to undergo in this region (below thetheoretical line 200) which can and will be for this essential purpose.The relative position of the top wire 40 is fairly well fixed by thebottoms of the closely spaced foils 51, 52, etc. which determine thelongitudinal contour of loci that will define the elongated curvepreviously set forth. The longitudinal (linear) speeds of the two wires20 and 40 are substantially equated by known wire drive control means(e.g. inter-connected drive motors M and M for any suitable drivingrolls such as the couch rolls 23 and 46, as schematically indicated inFIGURE 1C).

It has been found that the net effect of the high speed stock jet isthat it actually does not impact upon this downwardly moving wire 40until substantially the point P and thus does not generate within itself(the maximum and/or all of) the necessary (drainage) pressure untilapproximately this region, whereupon the elongated curve H=CD becomesimportant so that the internal stock body will feel the same pressurefor the next 6 to 8 inches during which the critically sensitive webformation takes place, and at substantially the end of this traveldistance (indicated in FIGURE 3 by distances from about D tosubstantially D to D the stock body has assumed, through its entireheight, a substantially uniform composition or consistency, which is notinconsistent with complete and final merging of the presently forming(or even formed) web bodies on the two wires and affords a more or lessfinal opportunity for the ultimate integration of the fibers collectedon each wire into a single web which does not have any readilyrecognized middle parting line. This permits the wires 20 and 40 tocontinue to move together, with continued dewatering of the webtherebetween, up to and including the couch press 23-47.

Thus, prior to the region of the elongated curve the object is to bringthe wires together generally in conformance with the contour of thecurve, and after the elongated curve the wires should be moved together,gradually, to effect water removal at increased pressure but without thenecessity of extreme caution in effecting the increased pressure. Thisis presumably because the network strength of the web is strong enoughafter the region of the elongated curve to resist damage at increasinglyhigher pressures and because there is no real network to damage ordestroy before the region of the elongated curve (because of thesubstantial dilution of the stock). In the critical region of theinstant elongated curve, however, the fiber network is commencing tobuild up on the top and bottom wires 40 and 20 over the distance fromabout D to substantially D to D and simultaneously the comparativelylower stock consistency (i.e. comparatively greater Water to fiberratio) intermediate these sensitive fiber networks on the top 40 andbottom wires 20 are responsive to pressure change between the wires andit is important to maintain temporarily a substantially constantpressure on such network or overall system on each wire until there is asubstantial equalization among the consistencies of such (with the moredilute stock being drained therethrough.

In this respect, the minimization of drastic pressure variations alongthe wire 40 is effected by the abruptly terminating off-running sides ofeach of the wire guiding foil edges 51a, 52a, etc. plus the overallslanted configuration of the foils 51, 52, etc. cooperating with theoverflow dam and the suction or subatmospheric pressure maintenancearrangement within the structure of the box 31 will all contribute tothe maintenance of such substantially constant pressure on the webnetwork on the wire 40; and in addition the selectivity and control ofrelative rates of dewatering between the two wires 40 and 20 afforded byvirtue of the limited tilting and/ or horizontal or vertical movement ofthe overall box 31 in conjunction with a corresponding pressureresponsive deflection in wire 20 plus adjustment of the alignment of thestock jet from the inlet 14b, all serve to assist in the aforesaidpressure control during the critical formation stages just described.

It will be appreciated that the stock consistency for newsprint (e.g. asmuch as 0.5% up to even 1.0%) is much greater than that of the so-calledtissue (e.g. which is in the lower range of about 0.1% to about 0.5%, byweight). Because of the extremely high speed which the tissue vehicle orwater goes through the forming wire, it will be appreciated that thecomparative rate at which a web is built upon the forming wire in atissue machine is so slow, that the present device may be used withgreat advantage on the tissue machine (but over a correspondinglygreater distance D). In other words, on the tissue machine theconsistency is so low that the rate of build up of a web or septum onthe wire is even less than (and certainly not more than) that whichoccurs in a machine having both top and bottom active wiressubject tovacuum, etc. Hence the elongated curved contour of the bottom wire on atissue machine (of the type disclosed in the application of E. J.Justus, filed Jan. 18, 1965 may have many, if not all, of the advantagesof the elongated curved top configuration of a top wire on the instantpreferably high consistency, e.g. newsprint machine), which because ofits lower consistency, not only tends preferably to conform to thedesired elongated curve along the top wire but also drives the bottomwire into a conforming noncircular-type curve.

It will be appreciated that the initial reach of bottom wire a from thebreast roll 22 to the foil 25 is otherwise unsupported (i.e. free ofrestraining means in contact therewith at locations opposite thepermeable stationary supporting surface of the box in the forming zone,as defined essentially by the foil or guide bottoms 51a, 52a, 53a, etc.)but under high tension such that the configuration of any curve thereinis nominal .(as compared to the elongated curved contour of the bottomof the foil box 39) although even theoretically such that neither a truecatenary nor a true beam deflection is obtained in the bottom wire.Instead, even though the initial forces applied to the bottom wire ofsaid tissue machine, as well as the instant bottom wire 20a, areconsiderably higher than those later applied (e.g. as the wire reach2G1! appoaches the foil 25) and this results in each case in anelongated-type curve which is definitely non-circular in configuration,but any such curve in the highly tensional bottom wire 20a is so nominalthat it is essentially theoretical, and not perceptible (visibly) as apractical matter. Of course, the same is true in the instant case inwhich the upper device is a suction-backed wire 40, rather than a felt,but the curve which the bottom wire tends to form is different, intheory and practice. In considering linear velocity conditions herein,it must be appreciated that, (1) in FIGURES 1, 2 and 3, the linearvelocity generally equated to the linear speed of the wires 20 and isactually based on fibers by weight (which go to make up the web);whereas (2) in the subsequent figures hereof we are concerned primarilywith linear stock velocities based on the whole volume of the verydilute stock. Since the weight of fibers coming through the jet 14 at agiven moment is only that required to make a very thin web, thecomparison therewith in terms of linear speed with the hereinafterso-called stock speed is difficult by virtue of the fact that the jet 14cross-section is substantially greater than that of the ultimate web,while also containing substantially greater volumes of water that willbe contained in the ultimate web.

In order to show additionally the preferred assembly hereof, thepreviously mentioned Parker et al. disclosure is shown in the subsequentviews hereof in the assembly of the invention in combination with thepreviously described forming section of FIGURES 1, 2 and 3.

In FIGURE 4 there is shown the essential concept of the preferred inletin the combination of the invention from a side elevational view withparts shown in section, showing primarily certain fundamental featuresof the instant inlet designated generally by the reference numeral it).These include generally closely spaced, laterally or cross-machineextending top 11' and bottom 12' walls which converge from a relativelythin (i.e. small in height) inlet 13', from which the walls 11' and 12extend longitudinally from right to left in the direction of stock flowin the device 10" a substantial distance convergingly, in fact, so as toconverge approximately at an angle of convergence of about 3, but whichmay range from a minimum practical angle of convergence of about 1 to amaximum practical angle of convergence of about 10, which angle ofconvergence is indicated in the schematic showing of FIGURE 6 as theangle B or as the total of the two halves indicated at B and B in FIGURE6. In general, the top and bottom walls 11' and 12' extend the fullwidth of the paper machine which may range from minimum commercialmachine sizes in the neighborhood of 100 to 150 inches to as much as themaximum known commercial machine sizes which are now in the neighbrohoodof about 340 or 350 inches. In contrast, the longitudinal dimension ofthese walls 11 and 12' in the direction of stock flow from the inlet 13to the very small outlet indicated at 14' in FIGURE 4, which outlet isreferred to in paper making as the slice, will ordinarily be only about40 to 50 inches, or something in the neighborhood of to A of thecross-machine dimension for the walls 11 and 12.

As the terms are used herein, transverse refers to the cross-machinedirection whereas longitudinal refers to the so-called machinedirection. The stock flows through the inlet portion defined between thegenerally converging walls 11' and 12' in a generally longitudinaldirection toward the slice 14', from which it flows (usually through aslight drop) onto a lower traveling forming surface 20 which is theusually very fine woven screen that is referred to in the paper machinetrade as the forming wire. The stock may thus be fed from the slice 14'onto the top of one forming wire 20* and between two converging formingWires 20, 40, in the type of forming device to be used. For the moment,we are concerned primarily with the inlet itself and the conversion ofthe stock flow from the initial generally transverse or cross-machineintroductory stock flow to an essentially longitudinal thin stream ofstock flowing through the slice 14' The stock (volume) velocity at theslice 14', being essentially the velocity of fibers as well as water atthe slice, is essentially the velocity of the forming wires 20, 40 andthus, as previously indicated in a paper machine operating at 2,400 feetper minute the linear velocity of stock at the slice 14 will beapproximately 40 feet per second. The slice 14' has a definite but verythin dimension as well as its very substantial transverse dimension.This thin dimension is generally perpendicular to the horizontal or tothe lower forming wire 20 itself, with respect to the alignment of thedimension, which is indicated schematically in FIGURE 6 as the dimensionA The dimension A is in effect the cross-sectional area (or at leastrepresentative of the cross-sectional area) of the slice 14' from whichthe stock flows between the forming wires at a linear velocity of, forexample, 40 feet per second. It will be appreciated that if we are toassume negligible frictional losses, then we may assume that the stocklinear velocity at any point in this inlet between the walls 11' and 12'will be approximately inversely proportional to the ratio between thecross-setcional area at the location in question and the cross-sectionalarea of the slice itself. Thus, referring to FIGURE 6, we see that thecross-sectional area of the slice is represented by the dimension Awhereas the cross-sectional area of the inlet previously described inconnection with FIGURE 4 as 13' is designated in FIGURE 6 by thereference letter A Assuming the back pressures on the stock flowing thefull longitudinal dimension of this portion of the inlet, which isgenerally considered to be the inlet channel R, is substantiallyconstant at all times, it can be assumed that the velocity of the stockin the longitudinal direction of flow in the region of the inlet A willbe 40 times A divided by A In other words, if the slice velocity is 40feet per second at a cross-sectional area of A then the stock velocitycoming into the channel R in the region A would be only 20 feet persecond if the dimension A is twice the dimension A which happens to beapprox imately the case, although in the preferred embodiment of theinstant invention the dimension A is actually closer to about threetimes the dimension A In any event, it is apparent from the showing inFIG- URE 4 and the schematic showing in FIGURE 6 that the top wall orroof 11 and the bottom wall or floor 12' converge gradually and thusthey impart to the stock a continuously increasing velocity over thelongitudinal dimension of the inlet channel R. It will also be notedthat the surface 12a of the floor or bottom wall 12 is a relativelysmooth straight surface that slopes downwardly slightly toward theforming wire 20 and the angle of slope is indicated at B schematicallyin FIGURE 6 with reference to the wire line WL, and it will be notedthat this angle of slope B (i.e., shown to be expressed in terms oftotal drop in the floor 12a, etc. of FIGURE 4 per substantially 5 to 10feet from A of FIGURE 6 to 14 of FIGURE 4 is preferably in theneighborhood of about /2 to 5 or even 10 inches) depending upon the typeof inlet desired. In general, the purpose of the inlet is to feed thestock through the slice 14' in generally substantially parallelalignment with respect to the bottom forming wire 20 so the floor 12ashould have only a very slight downward slope in the neighborhood ofabout 1 to 3 from the horizontal, and preferably about 2 as here shownin order to permit stock flow out of the inlet during shutdown and avoidthe collection of pools of stock on the surface of the floor 12a duringsuch shutdown of the device. Added to this convenience is the fact thatthe bump-like turbulence generators indicated in FIG- URE 4 generally at15 and 16 in the intermediate section R of the channel are mounted onlyon the roof of the channel. The forward section of the channel R isdefined between two relatively narrow wall sections of the roof 11B andthe floor 12B which provide a channel spacing indicated schematically inFIGURES 6 as A that is substantially equal for the full dimension ofthis exit 14, or terminal section R of the channel, although a nominaltaper (compared to that upstream) or reduction in the spacing A betweensuch smooth walls is not precluded and may even be helpful in the finalguidance of the stock jet at 14. As is indicated in FIGURE 4, the roofportion 11B is secured rather rigidly by suitable means such as welds orbolts (not shown) to the roof section 11C of the second section R of thechannel, by framing generally indicated at F and F such framing F and Fextending the full width of the machine and being connected by bolts orwelds (not shown) in such a manner as to afford a generally rigidconnection between the intermediate roof section 11C and the exit roofsection 11B, leaving the exit roof section 11B to extend in a generallycantilever type mounting longitudinally to the slice 14. It will benoted, however, that the slice extremity of the roof portion 11B isprovided with a plurality of ears, only one of which is shown at 17,each having pivotal connections 18' to rods 19 that are adjustablyconnected to a flange portion 20 on the framing F via twin lock nuts 21'and 22' which afford limited adjustment of the rod 19 longitudinally oraxially so as to aflord limited local adjustment of the relative spacingbetween the slice extremity of the roof wall portion 11B and the channelfloor portion opposite thereto designated 12B. This is for very minoradjustment of flow via very minor adjustment of the cross-sectional areain the local region, since the overall cross-sectional area in the finalexit section R of the inlet shown in FIGURE 4 is generally uniform andis designated schematically in FIGURE 6 as being generally of thedimension A throughout its entire transverse as well as longitudinaldimension.

The essential convergence of the walls 11' and 12 thus takes place atthe first channel section R and the second channel section R which arealready indicated as converging approximately along an angle ofconvergence B of about 3 to 5, and preferably about 3. In addition tothe limited adjustment for the final roof portion 11B via the rods 19-,it will be appreciated that the final roof portion 118 securely anchoredto the intermediate roof portion 11C is carried by a cross-machinepivot, indicated generally at 30' in FIGURE 4. The pivot 30 is carriedin mating blocks 30a and 30b carried on the forward end of a generallyrigid cross-machine frame element F which also carries the forward endof the roof portion 11D of the first channel section R The connectedcrossmachine framing sections F and F also have an car 31 carrying apivot 32 at opposite sides of the machine (only one of which being shownin FIGURE 4) which pivots 32 are connected through motors shownschematically at 33 to tie rods 34 which are in turn mounted on thefixed framing F by pivots 35'. The motor 33' is of conventionalstructure and is used to coact with the tie rods 34 to lift the forwardroof wall portions 11C and 11B simultaneously in and out of operatingposition and to leave open a corresponding fiat smooth merging sequenceof wall surfaces 12c and 12b which form the continuation of the floor12a for the bottom of the channel R from the inlet 13' down to the slice14- at the gradual slope of approximately 2 hereinbefore mentioned. Itwill thus be seen that the swinging of the roof portions 11C and 11B outof operating position will leave exposed an open smooth flat floor area12c'12b' which will not collect pools of stock and which can be readilyworked on to the extent required and will be readily exposed as a cleansmooth surface for this purpose. In this way the turbulence generators15' and 16' which will be described in detail hereinafter are moved outof operating position also and, by carrying these tur-bulence generators15 and 16' on the roof portion 11C which is swingable in and out ofoperating position, it is possible to make available a fiat floorsection 12c'-12b' available for immediate maintenance in the mostconvenient manner.

In contrast, in connection with the first channel portion or section Rit will be seen that turbulence generators are indicated generally at40' and 41 in the form of transversely extending rod banks, which willbe described in greater detail hereinafter, but which will be understoodto be defined by a multiplicity of relatively small abutments extendingbetween the walls 11' and 12 to afford support thereto and also toafford controlled reduction in the cross-sectional area in the immediatelocation thereof and further, it being generally rods, terminatingabruptly at the down stream end thereof for desired vortex turbulencegeneration in the stock flowing past such rodsv The upstream sides ofthe rods are smooth and rounded so as not to collect fibers or stringsthereon. This is the general structure of the rods in the banks 40' and41, which will be discussed in greater detail hereinafter, but which forthe moment will be described directly in connection with the overallsupport of the physical structure in that these rods 40' and 41 actuallymaintain the top and bottom walls 11 and 12 in the desired convergingclosely spaced relation hereinbefore described. Above this initialsection R it will be seen in FIGURE 4 that there is provided substantialreinforcement and additional framing including the upright framing F andadditional framing F thereabove which mounts the pivots 35 hereinbeforedescribed and which also mounts the initial stock inlet indicatedgenerally at 50 at the left end of FIGURE 4 and showing in thefragmentary view a definite level L also at the left hand side of FIGURE4.

The particular details of the framing F do not require additionaldescription, since the general nature of crossmachine framing andmounting of pivots such as the pivots 35 will be fully understood bythose skilled in the art. The cross-machine or transversely flowingstock 50' at the level L is indicated as the stock which enters theinlet 10' initially from one side of the machine and then flowsdownwardly through. a perforated body indicated generally at 51' whichactually constitutes a multiplicity of transversely spaced tubes onlyone of which 52' is shown in FIGURE 4. These tubes are shown as beingprovided with a suitable noncorrosive cylindrical liner 53' which ispreferably synthetic rubber or some other noncorrosive material that ismounted in cylindrical stainless steel spacers or backers 54 which aremounted in alignment with perforations in a top cross-beam 55' and abottom cross-beam 56 to complete the extension of the tubular conduits52, each of which have a substantial length-to-diametcr ratio of atleast 7:1 and preferably in the neighborhood of 10 to 15:1 or more,depending upon the space available for teh mounting of these tubes 52,Again, it will be appreciated that the essential concept of fiberdistribution within the individual tubes 52 by virtue of high velocitystock flow vertically downwardly therethrough is accomplished preferablyby the use of the length-to-diameter ratios specified. It will beappreciated that essentially there must be a stock jet generation inthis area in the form of a myriad or multiplicity of individual stockjets each of which will lie in a plane that is longitudinally alignedwith respect to the overall inlet. Thus the plane of the section shownin FIGURE 4 is longitudinally aligned and so will the planes be alignedwhich are parallel thereto and which pass through the respective axes ofthe successive transversely spaced tubes in the transverse seriesthereof. In general, the alignment of stock in the jet streams withinthe tubes 52' is the first step in converting the stock from thetransverse flow in the inlet 50' to flow in a longitudinal direction,even though the stock flows directly out of the tubes 52 and against thechannel floor at 12d to impinge thereon and develop lateral stock flowcomponents as well as additional longitudinal stock flow components inthe direction of the channel inlet 13'. The impingement of stock againstthe floor 12d which functions as a bafiie results in a general change indirection of stock flow of at least about (in this case substantially90) which effects by virtue of such impingement and turning of the stockstreams the required reconversion of lateral flow components in thestock so that the stock is spread laterally in such a manner that itwill tend to enter the channel inlet 13' at approximately the same or atleast a substantially uniform transverse pressure profile and overallstock linear velocity. It will be appreciated that the effects ofimpingement against the wall 12d and the immediate spreading of thestock in this chamber area will cause a rapid deceleration of stock flowfrom the point of view of linear velocity and will result in what mightbe considered heterogeneous rather than uniform stock flow components,but at the same time it will result in a spreading of the stock in sucha manner, under the particular condi' tions here involved, that theoverall stock pressure entering the very thin inlet end 13' of thechannel R will be generally uniform and at this stage we will haveapproximated a conversion from an essentially transverse orcross-machine stock flow to an essentially and generally uniformlongitudinal stock flow in a thin stream at the inlet 13.

Before going into further detail in connection with the nature of theturbulence generators hereinbefore noted in the succession 40', 41', 15and 16', reference is made to the overall cross-machine stock flow inletdevices in FIGURES 8, 9 and 10.

Referring first to FIGURE 9, it will be seen that the stock flows from afan pump FP', indicated only as an arrow for schematic purposes,upwardly through a vertical channel 60' and into a cross-machine channel61'. It will be noted that the general profile shown in FIGURE 8 isreally a top plan of FIGURE 9 of the channel 61' showing an enlargedinlet end 61a and a relatively narrow opposite end 61b. The channel 61'thus extends in a cross-machine direction but it diminishes incross-sectional area in the cross-machine direction.

As indicated in FIGURE 9, the overall cross-machine channel 61 need notbe built for stock recirculation therethrough and can simply be mountedon a structural arm 62 extending outwardly from the narrow end 61b andmounted on a conventional supporting pillar 63, while the inlet end6111' is also mounted on a corresponding supporting pillar 64 incorresponding manner so that the cross-machine channel 61' will bemaintained generally horizontal. It will also be noted that a source ofgas such as air A under pressure is shown diagrammatically being fedthrough a control valve CV into the top of the crossmachine channel 61so as to maintain a predetermined superatmospheric pressure on top ofthe level (L' of FIGURE 4) of the stock in the cross-machine channel61'. The combination of the taper or diminution in crosssectional areain the channel 51' and the superatmospheric air pressure maintained onthe top thereof will have the efiect of presenting stock to the top ofeach of the small perforations or mouths for the tubes (only two ofwhich are indicated at 52', 52' and dotted lines in FIGURE 9) so that agenerally uniform cross-machine pressure is exerted against the stock atthe mouth or tops of each of the tubes 52 and the stock jet or streamgenerated therein will thus be substantially uniform in velocity,volume, turbulence and other characteristics. These tubes 52, 52' willthen feed the stock into the channel R which is shown only from the rearin FIGURE 9' and then schematically in order to avoid confusing theview.

In an alternative embodiment also shown schematically, in FIGURE 10 iswill be seen that a fan pump FP1 feeds stock into the inlet side 71a ofa generally cylindrical tapered header 71 extending in cross-machinedirection toward a relatively narrow exit end 71b, from which a certainamount of stock is recirculated through the conduit indicated at 75'back into the inlet of the fan pump FP1' and makeup stock MS is also fedinto the inlet of the fan pump FP-l to maintain the desired amount oftotal stock entering the tapered cross-machine header 71'. The taperedcross-machine header 71 will thus provide by means of pressure controlfrom the fan pump FP-l and the effect of the gradually diminishingcross-sectional area of the body of the header 71' itself a generallytransversely uniform inlet pressure into the mouths 152a, 152a of themultiplicity of transversely spaced tubes, only two of which areindicated schematically at 152', 152' in FIGURE 10, so that the stockwill flow in jets downwardly into the channel inlet indicated in FIGURE10 as R400 corresponding to the channel R of FIG- URE 9.

Referring now generally to the overall stock velocities in the inlet 10shown schematically in FIGURE 6, it will be appreciated that referencemust be had first to what may be considered to be the controllingvelocity and that will be the velocity of the stock in the slice channelA which is approximately the linear velocity of the forming wire itself.Previously we have assumed a paper machine speed of 2,400 feet perminute which will mean a stock velocity at the slice A of 40 feet perminute. This will not necessarily determine the exact size or thicknessof the slice A here indicated schematically, because for certain weightsof paper a greater total volume of stock will be employed than in othercases. The linear velocity will be the same or substantially the samefor each paper machine speed, but the slice opening A will differ withdifferent weights of stock.

If we are to assume in terms of sixteenths of an inch that the thicknessof the slice A in this particular instance is substantially of an inchthen the crosssectional area indicated by the number 12 represents anumber of units which correspond in cross-sectional area to a linearvelocity of 40 feet per second. Using 12 as a reference, it will be seenthat the open area A in the region of the stock jets or tubes(hereinbefore described at 52') is comparatively limited and a highvelocity high pressure stock jet is desired in this area. Accordingly,the linear velocity in the tubes 52', expressed in terms of the overallopen area A will preferably range from about the slice speed to twicethe slice speed, or expressed in the numerical terminology, the arearatios A 'zA will range from 1:1 to 2:1 and are preferably about 12:7.This results in a veiy high stock velocity for impingement against thefloor extension 12d and for turning the stock jets through substantiallyat least about As previously mentioned, the best overall control of thestock jets is obtained by using a length-to-diameter ratio within thetubes 52' of at least about 7:1 and preferably 10 to 15:1 and actuallyup to about 25 or 30:1, depending to a great extent upon the limitationsof available space. In any event, better results are obtained usingratios of at least about 7:1 such that uniformity of stock flow in theindividual jets is obtained and the various other desirablecharacteristics in stock flow are obtained and maintained with greaterfacility. The impingement of these jets is preferably carried outagainst the floor 12d of the overall channel section R for the reasonthat this simplifies the structure and the stock then immediatelyimpinges upon the first set of turbulence generators 40 As indicated inFIGURE 4, the individual turbulence generators 40' and 41' in the twobanks are actually formed by through bolts 40a and 41a extending throughthe fioor 12 and in threaded engagement in the roof 11' seating inappropriate roof recesses annular locking devices 40b and 41b in theroof 11 (which are shown in full view for purposes of simplifying thedrawing) which provide the necessary annular recess to receive the topof the rod cover 40c and 410 which in each case is preferably anoncorrosive material such as a solid elastomer (i.e. synthetic rubberor a stainless steel material in the form of a tube which slopes overthe tie rods 40a and 41a and is mounted in the annular seating devices401) and 4112' so as to remain rigid and in clamped position duringoperation. The details of the individual rods 40' and 41' are directedessentially to the problems of convenient mounting and in the schematicview of FIG- URE 5, these details are not shown. FIGURE 5 is concernedprimarily with the concepts of turbulence generation. It will be seenfrom FIGURE 5 that, looking upwardly toward the roof as the view VV ofFIGURE 4 indicates, one Will note the discharges of the transverselyspaced tubes indicated at 52f, 52g and 52h in the bottom perforate platehereinbefore described by the reference numeral 56. Side channel wallsare, of course, provided, although only the single wall 57 is shown andthe end wall 58 is of course provided and is actually reinforced in thestructure of the instant device to hold the pressure. The tubes 52 areindicated as having diameters D which are spaced on centers M such thatthe overall open area is A which is described hereinbefore as beingpreferably an open area A equalling in total to from 50% to about of theslice cross-sectional area A In essence, the tubes 52' should haverelativelly small diameters in the neighborhood of about 1 inch andshould be approximately 12 inches in length so as to effect the desiredstock jet generation and this will result in their centers beingapproximately 2 inches apart in the spacing M herein indicated for thediameters D in FIGURE 5. The spacing arrangement can be changed and theopen area can be changed the-rein such that the diameters D may rangefrom /2 to 1 /2 inches and the spacing between the centers thereof mayrange from slightly more than D to as much as two or three times D Thesmaller the overall open area A in this region, the greater the jetvelocity impinging against the floor 12d. The stock impinges against thefloor 12d as indicated in FIGURE 4, and then makes the right angle turn.In making the right angle turn after impingement upon the floor 12d, itwill be appreciated that the stock flows into a chamber area having asubstantially greater cross-sectional area A which numerically speakingaffords a cross-sectional area ratio A 'zA ranging from about 7:20 to60, and is preferably about 7:40, which affords a deceleration of stockvelocity that averages such that the stock velocity is reduced from thejet velocity to about to Ms of the jet velocity in the initialimpingement, deceleration and turning chamber indicated schematically atR in FIGURE 6. The stock then proceeds into the inlet indicateddiagrammatically at A in such a manner as to have imposed on the stock aprimary velocity increase in the direction of the slice A by virtue ofthe converging walls.

The walls 11' and 12 preferably converge along a general angle ofconvergence of about 3 to 5, but under certain conditions this range maybe expanded to from 1 to It must be appreciated that a pair of closelyspaced walls 11' and 12' in the total absence of any turbulencegenerating devices 40, 41, 15', 16, etc. may extend for a verysubstantial longitudinal dimension (much greater than the approximately4 or 5 feet here shown) so as to impart to the stock a generally uniformcross-machine velocity profile as well as imparting the desiredturbulence within the stock itself. By cross-machine velocity profile,we refer to the longitudinal speed of stock at various cross-machinelocations in a given region such as along a plane taken through the lineA in FIG- URE 6. It is desirable to develop a generally uniformlongitudinal velocity component in the stock across the full width ofthe machine. It must be appreciated that initially the stock flowing inthe cross machine header 61' has no longitudinal velocity component atall. Even in the jet streams in the tubes 52, the forward longitudinalcomponent is 0, although the stock streams have been converted from across-machine direction to at least parallel planes in longitudinalalignment This is followed by impingement and then a series ofturbulence generating devices 40', 41', 15', 16, etc. or expressed inother words, a plurality of sequences wherein the stock will go throughcomparatively rapid maximum and minimum cross-sectional areas (from thetransverse cross-sectional area point of view) so as to superimpose uponthe overall generally increasing primary velocity a rather drasticsecondary velocity change in the stock. This secondary velocity changein each of these so-called sequences S S S S indicated in FIGURE 5 willin each case effect a certain amount of correction of the overallcross-machine velocity profile.

In the sequences herein described, it is preferable that at least thefirst two sequences S and S be defined by abutments which terminateabruptly at the downstream side so as to effect vortex turbulenegeneration and so as to e-fiiect relatively drastic turbulencegeneration, compared to that generated later on. Preferably this is doneusing a multiplicity of rod banks, in which banks each rod 40 403,4012', etc. will be generally cylindrical in form and in the case of thefirst sequence S will have approximately a diameter D of about 1 /2inches. The center spacing therebetween is preferably about twice thediameter hence M is preferably 2 times D in order to provide an openarea of approximately 50% and thus obtain the desired turbulence. As amatter of fact the open area may range from perhaps about 25% to 75%,but 50% has been found to be preferable and the particularcenter-to-center spacing M is also found to be significant in that theindividual rods or abutments in the first bank 40' will leave trailingwakes and this is desirable. The rods in the initial bank 40 are ofsubstantial size and are smoothly curved at their upstream ends so thatthey will not collect fibers, strings, or other matter and they willremain clean. This is very important from the point of view ofcontinuous operation of the device. In addition, they will generateturbulene (sometimes referred to as vortex-type turbulence) at thedownstream side thereof because they terminate abruptly at thedownstream sides of each of such rods (by virtue of their circularcross-section) and this turbulence will start to decay at theoff-running side of the first rod bank 40', but it will not havecompletely decayed within a dimension L which is preferably within therange of about two to five times M The preferred relationship betweenthe Center-to-center spacing of the rods or abutments in one bank andthe downstream spacing of the rods or abutments 41 in the second bank(i.e. the distance L is described in considerable detail in thepreviously mentioned application Ser. No. 228,621 and need not bedescribed in further detail herein. Essentially, the function involvesthat of having turbulence in a condition of partial but incomplete decayas the stock impinges upon the relatively smaller smooth round upstreamsurfaces of the rod bank 41, as indicated in connection with theindividual rods 41f, 41g, 4111', 411', etc. The individual rods 41 areabout 1 inch in diameter which is approximately a preferred size so thatthe relationship between the diameters D 'zD will be about 120.9 to 0.5and preferably about 3:2. The upstream rods are of comparatively largesize so that it will be possible to make sure that there will be nocollection of fibers or the like thereon. In addition, the upstreamfaces of these rods 40' will be continuously cleaned by the net effectof the impinging jets against the floor and the miscellaneous currentsin the stock generated thereby. This is the type of turbulencegeneration of rather substantial scale which is effected at this stagein the inlet at the stage indicated diagrammatically at A in FIGURE 6.As the stock approaches the oncoming side of the first bank of rods 40,it will be appreciated that the cross-sectional area of the channel Rhas diminished slightly to A but this diminution is not particularlysignificant. In the middle of the rod bank 40 extending transversely ofthe machine, however, it must be appreciated that there is a drasticreduction in overall crosssectional area A and as here shown this isapproximately a reduction. The net result will be a velocity increase inthe neighborhood of about as the stock moves from the location A at theoncoming side of the rod bank to the middle of the rod bank 40 at thelocation A and then as the stock completes the sequence S of the initialsequence herein described, the tock exits from the initial rod bank 40'and reaches a substantially greater cross-sectional area A4 indicated inFIGURE 6. It will be appreciated that the overall cross channelcrosssectional areas indicated by the units A ':A :A will in effectconstitute decreases in the neighborhood of ratios of approximately40:35 to 39:33 to 38, etc. so that there is a primary velocity increase,but there is a drastic reduction in cross-sectional area in the middleof the sequence S at A such that the open area or cross-sectional arearatio A :A will range from 4:1 to 4:3 and is preferably about 2:1, withvelocity changes in substantially the inverse ratio. In other words,with a velocity increase at the decreased cross-sectional area A Inreferring to the sequences 5 S etc. herein, it will be appreciated thateach sequence is in effect a cycle through which the stock is putsequentially from a minimum to a maximum and then to a minimum orconversely from a maximum then to a minimum and back to a maximumcross-sectional area. As here described schematically, each sequencegoes through the cycle from maximum to minimum to maximumcross-sectional area, and it will be appreciated that the second maximumcross-sectional area is slightly smaller than the first, in other wordsA, is a maximum that is slightly smaller than A because of the generalconvergence of the walls and the general reduction in cross-sectionalarea of the channel which is undergone during the overall longitudinalmovement of the stock through the channel.

It will also be appreciated that each sequence S S S S will have ageneral longitudinal dimension which is indicated schematically inFIGURE 5 in that it will involve the flow of stock approaching whateverthe turbulence generating device might be plus the flow of stock pastthe turbulence generating device and then the flow of stock into whatamounts to the subsequent maximum cross-sectional area, which for thesequence S involves the sequence shown schematically in FIGURE 6 as A AA The exact longitudinal dimension is not absolutely critical, but itmay be considered to be a dimension from approximately midway betweenone set of turbulence generators to midway between the next set ofturbulence generators, as in the case of the later sequences S2,, S3:S4-

The two rod banks 40 and 41 thus preferably have the same open areas andthis is preferably approximately a 50% open area so that there is aneffective doubling of the velocity at least in the secondary orsuperimposed stock velocity at each of the sequences 8, and S and theoverall turbulence generation is such that the second rod bank 41receives turbulence from the upstream rod bank 40 so as to keep theupstream faces of the rods 41' clean and permit the use of relativelysmaller diameter D rods in this bank.

Rather than having a multiplicity of smaller and smaller rods, whichmust necessarily in each case result in some trailing vortex turbulencegeneration because of the abrupt downstream termination of a rod by thevery nature of its construction, the instant inlet provides stillanother type of turbulence generation in the latter sequences S and S(i.e. at least the last two sequences) before the exit X.

As has previously been described, the exit chamber X is preferablydefined by a pair of smooth closely spaced walls that are generallyequidistant and effect whatever turbulence generation they are capableof effecting purely by virtue of the fact that the stock stream flowingthereby is moving at a very rapid rate and the walls are necessarilystanding still. This exit region X preferably has a longitudinaldimension that is at least as great as that of the last sequence S andpreferably at least as great as twice or more the longitudinal dimensionof the last sequence S In fact, in the arrangement here shown, the exitsection X' has a longitudinal dimension that is substantially threetimes that of the last sequence S This results in turbulence decay. Itis desired to obtain a certain amount of turbulence decay in the finalexit chamber. Actually the amount of turbulence decay will depend uponthe velocity of stock in the channel R. If the velocity is very slow,the turbulence generating devices will have to be more closely spacedand the exit chamber X will not be very long, because the benefit ofturbulence generation and defiocking will not want to be lostcompletely. On the other hand, if the stock speed is relatively higheven the closely spaced walls of the exit chamber X will impart acertain amount of turbulence and they will permit a great deal ofequalizing or generation of uniformity in the fiber distribution if theyare at least equal to two or three times the longitudinal dimension 8.,of the last sequence.

Referring to the sequences S and S it will be appreciated that theseturbulence generating devices are sheargenerators. In other words, theydo not rely solely on the vortex turbulence generation concept thatnecessarily results from the abrupt downstream ends of rods. Instead,they impart a general shearing effect to the stock stream.

Considering first the average velocity in the stock, it will beappreciated that as the stock moves from the position A to the positionA in FIGURE 6 it has already gone through two sequences S and S in whicha doubling of the stock velocity has been superimposed upon the primarygenerally increasing stock velocity by virtue of the two reductions incross-sectional area at the locations A and A The primary reduction incross-sectional area from A to A and thus the corresponding primaryincrease in stock velocity from A to A is in an approximate ratio of30:35 to 50. Preferably the ratio of A to A is about 4:3 and thevelocity increase is thus the inverse of this cross-sectional area ratioby the end of the second sequence S In the third and fourth sequences Sand S the cross-sectional areas go through the ranges A and A A inmaximum minimum maximum such that A is in a cross-sectional area ratioto A within the range of about A :A ranging from 4:1 to 4:3, butpreferably about 2:1. This again results in an approximatesuperimposition of double the velocity in the region A with almost ahalving of the velocity in the region A but followed by another doublingof the velocity in the second of these sequences 8, at the region A andfollowed again by almost a reduction in velocity at the off-running sideat A It will be appreciated that the general cross-sectional area ineach of the successive sequences S S S S involves a reduction, hence thegeneral velocity increases all the Way along. On top of this We have thesuper-imposition of drastic velocity changes by virtue of either theabutment turbulence generators 40 and 41 or the shear turbulencegenerators 15 and 16. The shear turbulence generators 15 and 16 generatea lower scale of turbulence but still give excellent fiber distributionand the desired fiber distribution for ultimate feeding to the exitchannel X.

As mentioned hereinbefore, the overall channel R could have the generalcharacteristics of the exit channel X if it had a great enoughlongitudinal dimension. The difficulty is that paper machines do notprovide for this much space. Accordingly, it is necessary to add to thedevice for converting the cross-machine stock flow into longitudinallydirected stock flow a certain number of turbulance generators which willgreatly diminish the overall exit stage dimension X. These variousturbulence generators 40, 41', 15 and 16 will not completely eliminatethe exit stage X but they will reduce the dimension thereof materiallyand make the size of the machine workable for practical purposes. Indeveloping turbulence generating systems which will do this, it has beenfound that at least the first two sequences S and S are preferably ofthe vortex generating type, as in the case of the rods 40 and 41;whereas it has also been found that preferably the last two sequenceshere designated S and S are preferably of the shear or approximatelyshear generating devices in the sense that a lower scale of turbulencewill be fed into the exit chamber X' and a better fiber distribution isultimately obtained at the slice 14'. Also, the drastic impingement inthe initial chamber R plus the vortex generation at the rods 40 and 41will cause complete breakup of fiber clots and the like so that therandom distribution of fibers in the stock that is desired will havebeen obtained, but the problem of maintaining this random distributionof fibers in the stock is not simple and also the problem of obtainingthe desired cross-machine profile for longitudinal stock velocity is notsimple and it has been found that these shearturbulence generatingdevices 15 and 16 are particularly useful at least as the last pair ofturbulence generators just before the exist chamber X. The importance ofthe exit chamber has already been discussed. The nature of shearturbulence generators 15' and 16 has been discussed in considerabledetail in, for example, the previously mentioned application Ser. No.69,338 which need not be described in complete detail, since this andthe other applications hereinbefore referred to are actuallyincorporated herein by reference. In essence, the purpose of a sheargenerator is to cause abrupt convergence followed by abrupt divergence(which would be from the area A to the area A during the abruptconvergence and from the area A to the area A for the abrupt divergencein such a manner as to superimpose an abrupt velocity change upon thestock (although this velocity change is actually at a rate that is fromA to perhaps )1 or the rate of velocity change that is imposed by theupstream rod banks 40' and 41). In addition, the purpose of sheargenerators is to minimize vortex type of turbulence generation byseparation of the stock from the walls during the downstream ordivergent flow of each sequence S and S Referring to the details ofFIGURE 7, it will be seen that the angle of convergence 15a between thesurface of the roof 11c and the turbulence generator 15' isapproximately an angle of 15 in the device here shown. This is arelatively abrupt angle of convergence and a more gradual angle could beused ranging perhaps down to as low as about 3 to 5 and up to as much asabout 20 for the more drastic conditions. On the other hand, the angleof divergence at the off-running side is of somewhat greater importancefrom the point of view of avoiding separation of the stock from thewall. In the turbulence generator 15' the angle of divergence 15b isalso here indicated as being about 15, although it may range from thisapproximate maximum down to as low as about 3 to 5 depending upon thespeed of stock.

Departing briefly from the mechanics of shear turbulence generation hereinvolved, it will be appreciated that as indicated in FIGURE 7, the roof110' is provided with a pair of cross-machine slots into which theanchoring portions 150 and 16c of the turbulence generators 15 and 16'may be slipped and retained for ordinary operation. These devices arethus moved in and out of position by sliding the same in the transverseor cross-machine direction which is a convenient arrangement. Theturbulence generators 15 and 16, however, extend the full width of thechannel section R and althouh they are shown in FIGURE 7 in full view itwill be appreciated that the longitudinal section at any location acrossthe machine will be the same. As indicated in FIGURE 6, the actualcross-sec tional dimension in the minimum area A is slightly smallerthan in the minimum area A and in each case these dimensions are in aratio to the dimension A of approximately 1:4 to 3:4, so the velocitiesat the locations A and A are actually greater than the slicelongitudinal stock velocity and this is desired for purposes ofimparting a final shearing force to the stock approaching the slice 14'.As previously indicated, the floor 12c in the second section R is atapproximately an angle of about 2 to the horizontal or to the wire lineindicated by the line marked W in FIGURE 7. The roof 110 which is acontinuation of the roof 11a of the first section R in the operatingarrangement is approximately at an angle of about 5 or 5% to the wireline W, so that the angle of convergence in the preferred embodimenthere shown is slightly over 3. This means that the centerline plane forthe channel R is a line indicated generally at P--P', which is really acenterline plane PP that is used essentially for reference purposes. Itwill be seen that the convergence and divergence in the stock streamcreated by the shear generators 15' and 16 is not symmetrical withrespect thereto and this seems to impart an improvement in the overallfiber distribution. In addition, it affords the mounting of theturbulence generators 15' and 16' only on the roof so that they may beswung in and out of operating position during maintenance and at othercenvenient times while still carrying out their essential and completefunction when in operating position. The peak for the first of thesesequences S is the peak indicated at the apex of the triangmlarconfiguration at 150." for the shear turbulence generator 15'. This isnot a sharp peak but a generally rounded peak and it is positioned adistance L (FIGURE 5) that is approximately within the range of 2 to 5times the dimension M which is the center-to-center spacing in theupstream vortex turbulence generating rod bank 41', so that theconvergence will be maximized at the region of incomplete turbulencedecay from the upstream turbulence generating device, which in this caseis the rod bank 41'. The same is true of the peak 16d for the downstreamshear generator in that it also results in maximum stock convergence ata region of only partial decay from the upstream turbulence generator15.

With respect to the problem of shear generation, it must be appreciatedthat purely shear-turbulence generation does not permit any separationof the stock from the wall during the divergent flow. Thus in the regiondesignated 15c and in the subsequent region of divergence designated16s, the rapid flow of stock past the shear turbulence generators 15'and 16, respectively, preferably does not result in separation from thechannel walls or the channel roof lie in this instance. It is known thatin the case of relatively high speeds pure water will separate from adivergent wall if the angle of divergence from the centerline or centerplane of the channel is greater than about 7. In other words, in thecase of pure water, if the angle indicated at 15c and 16e' were greaterthan 7, there would be separation of the pure water from the oftrunningside of the generators 15' and 16'. The angle of divergence 15c and 16sis represented in relation to the center plane P'P' and the divergenttrailing face 151) and 16b for the generators 15' and 16' respectively,and it will be appreciated that in the construction here shown theseangles of divergence 15c and 16e' are at the maximum or perhaps somewhatabove the maximum tolerated angle of divergence to completely avoidseparation. It is known that stock with even relatively smallpercentages of fiber there in does not behave like pure Water and itdoes not behave like a true fluid or liquid. Instead, it haspeculiarities in behavior and it will not separate from the Wall at anangle of divergence immediately above 7, in fact, angles of divergenceas high as 12', 13 or even 14 are permitted. In the present instancesimple arithmetic will reveal that the angle of divergence 152' and 16e'is approximately 13 /2 in each case. This is about the maximum toleratedfor practical purposes. It may result in a slight amount of separationbut it does not result in a significant amount of separation or aharmful amount of separation, particularly in view of the fact that theexit channel X is at least twice and preferably three times thelongitudinal dimension 8., of the last sequence of shear turbulencegeneration. In other words, these turbulence generators 15 and 16' aredesigned to obtain the maximum desired turbulence under thecircumstances without causing any undesirable results at the ultimateslice 14' and this is done by using a rather drastic angle ofdivergence, preferably, in conjunction with a reasonably long exitchannel X' which has the description already given. It will beappreciated that the angle of divergence may be reduced from theindicated 13 or 14 down to as low as 3, 5 or 6 in certain instances andin the case of certain types of stock this is not a difficult problemsince the generators 15' and 16' may be readily constructed so as toreduce this angle of divergence. The type of shear turbulence generator15' and 16' here shown readily accommodates this type of change sincethe variable involves nothing more than adding to or subtracting fromthe material employed in the off-running side of the turbulencegenerator relative to the center plane PP' of the channel. Thus thechannel itself may have its angle of convergence increased or decreasedsomewhat under certain circumstances, and this will involve a rathermajor change in the overall structure. On the other hand, by verynominal and relatively easily made changes the shear generators 15 and16' may be altered to obtain whatever angle of divergence 152 and 162may be desired or may be found to be desirable. Also, it will be notedthat at the approach to the channel X there is a slight reduction from Ato A in cross-sectional area and the stock does pass a rounded edge,indicated at X in FIGURE 7 so as to obtain a slight additionalturbulence generation by virtue of the rather abrupt change incross-sectional area and thus abrupt velocity change at this very point.Moreover, a taper (involving an overall decrease in A of no more thanthe decrease at X between the generally parallel smooth walls in theelongated section R may effect therein a gradual helpful velocityacceleration in the final stock jet. This serves to cooperate with thedownstream sequence 8., to afford the best fiber distribution and thebest results in high speed machines.

As previously mentioned the slice jet 14' is so positioned as to besubstantially aimed at the previously re-

